1. World Health Organization. Health topic poliomyelitis (polio). Geneva: WHO; April 2016, Available at: http://www.who.int/topics/poliomyelitis/en/.(accessed June 26, 2015)
2. Centers for Disease Control and Prevention. Global health, polio. Atlanta, GA: CDC; Oct 2014, Available at: http://www.cdc.gov/polio/about/index.htm.(accessed June 26, 2015)
3. Surviving polio in a post-polio world;Groce;Soc Sci Med,2014
4. Global Polio Eradication Initiative. Polio and prevention: history of polio. GPEI; 2010, Available at http://www.polioeradication.org/Polioandprevention/Historyofpolio.aspx.(accessed June 30, 2015)
5. Refusal of oral polio vaccine in northwestern Pakistan: a qualitative and quantitative study;Murakami;Vaccine,2014